FIG. 1 is a schematic representation of an aircraft engine 10 attached to a pylon 13, according to a first attaching means generally applied in prior art. In the description that follows, by X, it is meant the longitudinal direction of the pylon 13, which can also be considered as the longitudinal direction of the engine 10, the direction X being parallel to a longitudinal axis 18 of the engine 10. On the other hand, by Y, it is meant the direction directed transversally to the pylon 13 and that can also be considered as the transverse direction of the engine 10, and Z the vertical direction, these three directions X, Y and Z being orthogonal between each other. Moreover, the terms “front” and “back” are to be considered with respect to a direction of advance of the aircraft experienced as a result of a thrust exerted by the engine 10, this direction being schematically represented by an arrow 19. The engine 10 has available a fan casing 11 having a great dimension, and includes in the rear a turbine casing 12 having a smaller dimension. The fan casing 11 and the turbine casing 12 are of course integral with each other. The fan casing 11 is cylindrically shaped, said cylinder extending along the axis X. The pylon 13, also called strut, enables the engine 10 to be suspended beneath the wings 14 of the aircraft. The pylon 13 actually forms the interface between the engine 10 and the wings 14. The pylon 13 also enables strains generated by the engine 10 to be transmitted to the structure of the aircraft, and allows fuel, electrical, hydraulic and pneumatic systems to be conveyed between the engine 10 and the aircraft. The engine 10 is provided with a system for attaching the engine 10 to the pylon 13, which is interposed between the engine 10 and a lower face 15 of the pylon 13. The attaching system includes a front engine fastener 16 and a back engine fastener 17. The front engine fastener 16 connects the fan casing 11 to the lower face 15 of the pylon 13, and the back engine fastener 17 connects the turbine casing 12 to the lower face 15 of the pylon 13.
FIG. 2 is a perspective view of the front engine fastener 16. The front engine fastener 16 includes a suspension beam 21 lying on a coat hanger 22, and connected thereto through hinged connecting rods 23. The suspension beam 21 includes a planar upper face 24, intended to be in contact and attached via bolts to the lower face 15 of the pylon 13. The coat hanger 22 is curved in shape to accurately conform to the cylindrical shape of the fan casing 11, and is attached to the same via bolts.
FIGS. 3a, 3b and 3c represent the different steps of mounting the engine 10 to the pylon 13, said pylon 13 being secured to the wings 14. The elements of said figures are represented along a plane YZ. In FIG. 3a, the engine 10 lies on the ground. The front engine fastener 16 is attached to the fan casing 11 of the engine 10. Hoisting harnesses 30 are secured on the one end to the wings 14, and on the other hand to the fan casing 11. The vertical hoisting of an aircraft engine using hoisting harnesses is a method well known by those skilled in the art. In FIG. 3b, the engine 10 is being vertically hoisted through the hoisting harnesses 30. In FIG. 3c, the upper face 24 of the front engine fastener 16 is pressed against the lower face 15 of the pylon 13, and attached to the same via bolts 31.
Such an attachment of the engine 10 to the pylon 13 results in a space between the engine 10 and the pylon 13. The height of said space is the height of the front engine fastener 16, since the height of the fan casing 11 is higher than the height of the turbine casing 12. But, for aerodynamic reasons, it is attempted to bring the engine 10 as close as possible to the pylon 13. This indeed enables the aerodynamic drag of the pylon 13 to be decreased and engines to have a higher FAN diameter.
To overcome this drawback, a solution wherein a front engine fastener and a method for mounting an engine onto a pylon, such that said front engine fastener is attached to the front face of the pylon, and no longer to a lower face of the pylon, was suggested. Thus, the space between the engine and the pylon can be decreased. The mounting method disclosed consists in vertically hoisting the engine using hoisting harnesses, up to have four though openings provided in the front engine fastener coincide, with four bores provided in the front face of the pylon, and then inserting a shear pin into each of the apertures thus formed. The front engine fastener is thus attached to the front face of the pylon using fours shear pins and bolts.
However, the mounting method thus described is complicated because inserting a shear pin through an opening of the front engine fastener, and then through a bore of the pylon, requires great positioning accuracy of the front engine fastener towards the pylon, in particular since the operation should be repeated four times, for each of the four shear pins to be inserted. For this, the time for mounting the engine to the pylon is long.